Restricted expression of the hyaluronan receptor, CD44, during postimplantation mouse embryogenesis suggests key roles in tissue formation and patterning

Exploring the Role of Hyaluronic Acid in Reproductive Biology and Beyond: Applications in Assisted Reproduction and Tissue Engineering

Hyaluronic acid (HA) plays a prominent role in various aspects of reproductive biology and assisted reproductive technologies (ART). This review describes the multifaceted influence of HA, ranging from primordial germ cell migration, ovarian follicle development, and ovulation in females to sperm structure, physiology, motility, and capacitation in males. In addition, HA also plays an important role in fertilization and promotes embryo implantation by mediating cellular adhesion and communication within the uterus. Against this physiological background, the review examines the current applications of HA in the context of ART. In addition, the article addresses the emerging field of reproductive tissue engineering, where HA-based hydrogels offer promising perspectives as they can support the development of mature oocytes and spermatogenesis in vitro. Overall, this review highlights the integral role of HA in the intricate mechanisms of reproductive biology and its growing importance for improving ART outcomes and the field of tissue engineering of the reproductive system.

GDF-8 improves in vitro implantation and cryo-tolerance by stimulating the ALK5-SMAD2/3 signaling in bovine IVF embryo development

Transforming growth factor-beta (TGF-β) plays a critical role in regulating trophoblast invasion and proliferation. Growth differentiation factor-8 (GDF-8) is a member of the TGF-β superfamily and is categorized as a myostatin subtype. It is primarily a secreted protein synthesized in skeletal muscle cells. It is expressed in the placenta, reproductive tissues, and cells. In this study, we investigated the role of GDF-8 in the development and hatching rate of bovine embryos. We noted a notable elevation (p < 0.05) in the development and hatching rates compared to the control embryos. Furthermore, the GDF-8 group showed a significantly improved total cell number (p < 0.05) and an increase in trophectoderm ratio inner cell mass (trophectoderm: inner cell mass) cells (p < 0.001) compared to the control group. Additionally, blastocysts treated with GDF-8 exhibited significantly higher mRNA levels of caudal-type homeobox 2 (CDX2) (p < 0.05). The trophoblast invasion area was significantly larger in the GDF-8 group than in the control group (p < 0.01). Furthermore, qRT-PCR analysis revealed significantly higher mRNA levels (p < 0.05) of matrix metalloproteinases 9 (MMP9) and follistatin-like 3(FSTL3), both of which are associated with the ALK5-SMAD2/3 signaling pathway, in the GDF-8 group than those in the control group. The mRNA expression levels of genes related to tight junctions (TJ) and adherent junctions were higher in the GDF-8 group than those in the control group (p < 0.05). After 24 h of thawing, blastocysts were analyzed using 4-kDa FITC-dextran, which revealed a higher TJ integrity in the GDF-8 group (p < 0.01). Thus, GDF-8 plays a crucial role in bovine embryonic development, in vitro implantation, and cryotolerance.

Transcriptome Profiling Identifies Differentially Expressed Genes in Skeletal Muscle Development in Native Chinese Ducks

China boasts a rich diversity of indigenous duck species, some of which exhibit desirable economic traits. Here, we generated transcriptome sequencing datasets of breast muscle tissue samples from 1D of four groups: Pekin duck pure breeding group (P), Jinling White duck breeding group (J), P ♂ × J ♀ orthogonal group (PJ) and J ♂ × P ♀ reciprocal-cross group (JP) (n = 3), chosen based on the distinctive characteristics of duck muscle development during the embryonic period. We identified 5053 differentially expressed genes (DEGs) among the four groups. Network prediction analysis showed that ribosome and oxidative phosphorylation-related genes were the most enriched, and muscular protein-related genes were found in the 14-day-old embryonic group. We found that previously characterized functional genes, such as FN1, AGRN, ADNAMST3, APOB and FGF9, were potentially involved in muscle development in 14-day-old embryos. Functional enrichment analysis suggested that genes that participated in molecular function and cell component and key signaling pathways (e.g., hippo, ribosome, oxidative phosphorylation) were significantly enriched in the development of skeletal muscle at 14 days of embryonic age. These results indicate a possible role of muscle metabolism and myoglobin synthesis in skeletal muscle development in both duck parents and hybrids.

The (intra-aortic) hematopoietic cluster cocktail: what is in the mix?

The adult-definitive hematopoietic hierarchy and hematopoietic stem cells (HSCs) residing in the bone marrow are established during embryonic development. In mouse, human, and many other mammals, it is the sudden formation of so-called intra-aortic/arterial hematopoietic clusters (IAHCs) that best signifies and visualizes this de novo generation of HSCs and hematopoietic progenitor cells (HPCs). Cluster cells arise through an endothelial-to-hematopoietic transition and, for some time, express markers/genes of both tissue types, whilst acquiring more hematopoietic features and losing endothelial ones. Among several hundreds of IAHC cells, the midgestation mouse embryo contains only very few bona fide adult-repopulating HSCs, suggestive of a challenging cell fate to achieve. Most others are HPCs of various types, some of which have the potential to mature into HSCs in vitro. Based on the number of cells that reveal hematopoietic function, a fraction of IAHC cells is uncharacterized. This review aims to explore the current state of knowledge on IAHC cells. We will describe markers useful for isolation and characterization of these fleetingly produced, yet vitally important, cells and for the refined enrichment of the HSCs they contain, and speculate on the role of some IAHC cells that are as-yet functionally uncharacterized.

Recursive Feature Elimination-based Biomarker Identification for Open Neural Tube Defects

Background: Open spina bifida (myelomeningocele) is the result of the failure of spinal cord closing completely and is the second most common and severe birth defect. Open neural tube defects are multifactorial, and the exact molecular mechanism of the pathogenesis is not clear due to disease complexity for which prenatal treatment options remain limited worldwide. Artificial intelligence techniques like machine learning tools have been increasingly used in precision diagnosis. Objective: The primary objective of this study is to identify key genes for open neural tube defects using a machine learning approach that provides additional information about myelomeningocele in order to obtain a more accurate diagnosis. Materials and Methods: Our study reports differential gene expression analysis from multiple datasets (GSE4182 and GSE101141) of amniotic fluid samples with open neural tube defects. The sample outliers in the datasets were detected using principal component analysis (PCA). We report a combination of the differential gene expression analysis with recursive feature elimination (RFE), a machine learning approach to get 4 key genes for open neural tube defects. The features selected were validated using five binary classifiers for diseased and healthy samples: Logistic Regression (LR), Decision tree classifier (DT), Support Vector Machine (SVM), Random Forest classifier (RF), and K-nearest neighbour (KNN) with 5-fold cross-validation. Results: Growth Associated Protein 43 (GAP43), Glial fibrillary acidic protein (GFAP), Repetin (RPTN), and CD44 are the important genes identified in the study. These genes are known to be involved in axon growth, astrocyte differentiation in the central nervous system, post-traumatic brain repair, neuroinflammation, and inflammation-linked neuronal injuries. These key genes represent a promising tool for further studies in the diagnosis and early detection of open neural tube defects. Conclusion: These key biomarkers help in the diagnosis and early detection of open neural tube defects, thus evaluating the progress and seriousness in diseases condition. This study strengthens previous literature sources of confirming these biomarkers linked with open NTD's. Thus, among other prenatal treatment options present until now, these biomarkers help in the early detection of open neural tube defects, which provides success in both treatment and prevention of these defects in the advanced stage.

Heterogeneity in endothelial cells and widespread venous arterialization during early vascular development in mammals

Arteriogenesis rather than unspecialized capillary expansion is critical for restoring effective circulation to compromised tissues in patients. Deciphering the origin and specification of arterial endothelial cells during embryonic development will shed light on the understanding of adult arteriogenesis. However, during early embryonic angiogenesis, the process of endothelial diversification and molecular events underlying arteriovenous fate settling remain largely unresolved in mammals. Here, we constructed the single-cell transcriptomic landscape of vascular endothelial cells (VECs) during the time window for the occurrence of key vasculogenic and angiogenic events in both mouse and human embryos. We uncovered two distinct arterial VEC types, the major artery VECs and arterial plexus VECs, and unexpectedly divergent arteriovenous characteristics among VECs that are located in morphologically undistinguishable vascular plexus intra-embryonically. Using computational prediction and further lineage tracing of venous-featured VECs with a newly developed Nr2f2CrexER mouse model and a dual recombinase-mediated intersectional genetic approach, we revealed early and widespread arterialization from the capillaries with considerable venous characteristics. Altogether, our findings provide unprecedented and comprehensive details of endothelial heterogeneity and lineage relationships at early angiogenesis stages, and establish a new model regarding the arteriogenesis behaviors of early intra-embryonic vasculatures.

Pre-configuring chromatin architecture with histone modifications guides hematopoietic stem cell formation in mouse embryos

The gene activity underlying cell differentiation is regulated by a diverse set of transcription factors (TFs), histone modifications, chromatin structures and more. Although definitive hematopoietic stem cells (HSCs) are known to emerge via endothelial-to-hematopoietic transition (EHT), how the multi-layered epigenome is sequentially unfolded in a small portion of endothelial cells (ECs) transitioning into the hematopoietic fate remains elusive. With optimized low-input itChIP-seq and Hi-C assays, we performed multi-omics dissection of the HSC ontogeny trajectory across early arterial ECs (eAECs), hemogenic endothelial cells (HECs), pre-HSCs and long-term HSCs (LT-HSCs) in mouse embryos. Interestingly, HSC regulatory regions are already pre-configurated with active histone modifications as early as eAECs, preceding chromatin looping dynamics within topologically associating domains. Chromatin looping structures between enhancers and promoters only become gradually strengthened over time. Notably, RUNX1, a master TF for hematopoiesis, enriched at half of these loops is observed early from eAECs through pre-HSCs but its enrichment further increases in HSCs. RUNX1 and co-TFs together constitute a central, progressively intensified enhancer-promoter interactions. Thus, our study provides a framework to decipher how temporal epigenomic configurations fulfill cell lineage specification during development.

The tissues and regulatory pattern of limb chondrogenesis

Initial limb chondrogenesis offers the first differentiated tissues that resemble the mature skeletal anatomy. It is a developmental progression of three tissues. The limb begins with undifferentiated mesenchyme-1, some of which differentiates into condensations-2, and this tissue then transforms into cartilage-3. Each tissue is identified by physical characteristics of cell density, shape, and extracellular matrix composition. Tissue specific regimes of gene regulation underlie the diagnostic physical and chemical properties of these three tissues. These three tissue based regimes co-exist amid a background of other gene regulatory regimes within the same tissues and time-frame of limb development. The bio-molecular indicators of gene regulation reveal six identifiable patterns. Three of these patterns describe the unique bio-molecular indicators of each of the three tissues. A fourth pattern shares bio-molecular indicators between condensation and cartilage. Finally, a fifth pattern is composed of bio-molecular indicators that are found in undifferentiated mesenchyme prior to any condensation differentiation, then these bio-molecular indicators are upregulated in condensations and downregulated in undifferentiated mesenchyme. The undifferentiated mesenchyme that remains in between the condensations and cartilage, the interdigit, contains a unique set of bio-molecular indicators that exhibit dynamic behaviour during chondrogenesis and therefore argue for its own inclusion as a tissue in its own right and for more study into this process of differentiation.

Immunohistochemical profile of CD markers in experimental neural tube defect

Neural tube defects (NTDs) are the second most common birth defects worldwide. Stem cells play a critical role in the mechanisms underlying NTDs. We established an experimental NTD model in rats using retinoic acid (RA). We used mesenchymal and hemopoietic stem cell markers to determine their distribution in the mesenchyme in and around the neuroepithelium during the embryonic and fetal periods in both cranial and caudal regions. Adult female rats were given RA on days 5 and 10 of gestation and olive oil was administered to the control group. On days 10.5 and 15.5, embryos in the experimental and control groups were removed from the uterus. Embryos were embedded in paraffin and serial sections of the cranial and caudal neural tube were examined. We found severe cranial and caudal defects including axial rotation in the experimental groups using histochemistry. We used CD44, CD56, CD73, CD90, CD105, CD271 antibodies as mesenchymal stem cell markers and CD14, CD45 as hemopoietic stem cell markers. More CD44, CD56, CD90, CD105 and CD14 were detected during the embryonic period than the fetal period. CD73 was more frequent during the fetal period, whereas CD271 and CD45 were not significantly different. When CD44, CD56, CD73, CD90, CD105, CD271 immunostaining was found, NTDs were decreased early and increased later. We found no significant difference between CD14 and CD45. Formation of NTDs was due to deterioration of the of the neuroepithelial and surrounding stem cells. One reason for the formation of NTDs is that stem cells may develop defective cell-cell or cell-matrix interactions.

cd44 deletion suppresses atypia in the precancerous mouse testis

Loss-of-function of RHAMM causes hypofertility and testicular atrophy in young mice, followed by germ cell neoplasia in situ (GCNIS) of the testis, cellular atypia, and development of the testicular germ cell tumor (TGCT) seminoma. These pathologies reflect the risk factors and phenotypes that precede seminoma development in humans and-given the high prevalence of RHAMM downregulation in human seminoma-link RHAMM dysfunction with the aetiology of male hypofertility and GCNIS-related TGCTs. The initiating event underlying these pathologies, in RHAMM mutant testis, is premature displacement of undifferentiated progenitors from the basal compartment. We hypothesized that cd44 (both cancer initiating cell- and oncogenic progression marker) will drive GCNIS development, induced by RHAMM-loss-of-function in the mouse. We report that cd44 is expressed in a specific subset of GCNIS testes. Its genetic deletion has no effect on GCNIS onset, but it ameliorates oncogenic progression. We conclude that cd44 expression, combined with RHAMM dysfunction, promotes oncogenic progression in the testis.

Impact of oocyte-secreted factors on its developmental competence in buffalo

Oocyte-secreted factors (OSFs) play an important role in the acquisition of oocyte developmental competence through bidirectional cross-talk between oocyte and cumulus cells via gap junctions. Thus, the present study was designed to investigate the effect of two OSFs, growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15), on the developmental competence of buffalo oocytes derived from two different follicle sizes. Cumulus–oocyte complexes (COCs) from large follicles (LF, >6 mm) or small follicles (SF, <6 mm) were collected and matured in vitro either in the presence of GDF9 or BMP15, or both, or with the denuded oocytes (DOs) as a source of native OSFs. Cleavage and blastocyst rates were significantly (P < 0.05) higher in LF-derived than SF-derived oocytes. Cleavage and blastocyst rates were significantly higher (P < 0.05) in the DOs and the combination groups compared with the control, GDF9 alone and BMP15 alone groups, both in LF-derived and SF-derived oocytes, although the cleavage and blastocyst rates did not differ significantly (P > 0.05) between DOs and combination groups. Relative mRNA analysis revealed significantly higher (P > 0.05) expression of the cumulus cell marker genes EGFR, HAS2, and CD44 in LF-derived than SF-derived oocyte; the expression of these markers was significantly higher (P > 0.05) in DOs and combination groups, irrespective of the follicle size. These results suggested that LF-derived oocytes have a higher developmental competence than SF-derived oocytes and that supplementation of GDF9 and BMP15 modulates the developmental competence of buffalo oocytes by increasing the relative abundance of cumulus-enabling factors and thereby increasing cleavage and the quality of blastocyst production.

Epidermal-specific deletion of CD44 reveals a function in keratinocytes in response to mechanical stress

CD44, a large family of transmembrane glycoproteins, plays decisive roles in physiological and pathological conditions. CD44 isoforms are involved in several signaling pathways essential for life such as growth factor-induced signaling by EGF, HGF or VEGF. CD44 is also the main hyaluronan (HA) receptor and as such is involved in HA-dependent processes. To allow a genetic dissection of CD44 functions in homeostasis and disease, we generated a Cd44 floxed allele allowing tissue- and time-specific inactivation of all CD44 isoforms in vivo. As a proof of principle, we inactivated Cd44 in the skin epidermis using the K14Cre allele. Although the skin of such Cd44^Δker mutants appeared morphologically normal, epidermal stiffness was reduced, wound healing delayed and TPA induced epidermal thickening decreased. These phenotypes might be caused by cell autonomous defects in differentiation and HA production as well as impaired adhesion and migration on HA by Cd44^Δker keratinocytes. These findings support the usefulness of the conditional Cd44 allele in unraveling essential physiological and pathological functions of CD44 isoforms.

Primary Bovine Extra-Embryonic Cultured Cells: A New Resource for the Study of In Vivo Peri-Implanting Phenotypes and Mesoderm Formation

In addition to nourishing the embryo, extra-embryonic tissues (EETs) contribute to early embryonic patterning, primitive hematopoiesis, and fetal health. These tissues are of major importance for human medicine, as well as for efforts to improve livestock efficiency, but they remain incompletely understood. In bovines, EETs are accessible easily, in large amounts, and prior to implantation. We took advantage of this system to describe, in vitro and in vivo, the cell types present in bovine EETs at Day 18 of development. Specifically, we characterized the gene expression patterns and phenotypes of bovine extra-embryonic ectoderm (or trophoblast; bTC), endoderm (bXEC), and mesoderm (bXMC) cells in culture and compared them to their respective in vivo micro-dissected cells. After a week of culture, certain characteristics (e.g., gene expression) of the in vitro cells were altered with respect to the in vivo cells, but we were able to identify "cores" of cell-type-specific (and substrate-independent) genes that were shared between in vitro and in vivo samples. In addition, many cellular phenotypes were cell-type-specific with regard to extracellular adhesion. We evaluated the ability of individual bXMCs to migrate and spread on micro-patterns, and observed that they easily adapted to diverse environments, similar to in vivo EE mesoderm cells, which encounter different EE epithelia to form chorion, yolk sac, and allantois. With these tissue interactions, different functions arose that were detected in silico and corroborated in vivo at D21-D25. Moreover, analysis of bXMCs allowed us to identify the EE cell ring surrounding the embryonic disc (ED) at D14-15 as mesoderm cells, which had been hypothesized but not shown prior to this study. We envision these data will serve as a major resource for the future in the analysis of peri-implanting phenotypes in response to the maternal metabolism and contribute to subsequent studies of placental/fetal development in eutherians.

Myocardial extracellular matrix: an ever-changing and diverse entity

The cardiac extracellular matrix (ECM) is a complex architectural network consisting of structural and nonstructural proteins, creating strength and plasticity. The nonstructural compartment of the ECM houses a variety of proteins, which are vital for ECM plasticity, and can be divided into 3 major groups: glycoproteins, proteoglycans, and glycosaminoglycans. The common denominator for these groups is glycosylation, which refers to the decoration of proteins or lipids with sugars. This review will discuss the fundamental role of the matrix in cardiac development, homeostasis, and remodeling, from a glycobiology point of view. Glycoproteins (eg, thrombospondins, secreted protein acidic and rich in cysteine, tenascins), proteoglycans (eg, versican, syndecans, biglycan), and glycosaminoglycans (eg, hyaluronan, heparan sulfate) are upregulated on cardiac injury and regulate key processes in the remodeling myocardium such as inflammation, fibrosis, and angiogenesis. Albeit some parallels can be made regarding the processes these proteins are involved in, their specific functions are extremely diverse. In fact, under varying conditions, individual proteins can even have opposing functions, making spatiotemporal contribution of these proteins in the rearrangement of multifaceted ECM very hard to grasp. Alterations of protein characteristics by the addition of sugars may explain the immense, yet tightly regulated, variability of the remodeling cardiac matrix. Understanding the role of glycosylation in altering the ultimate function of glycoproteins, proteoglycans, and glycosaminoglycans in the myocardium may lead to the development of new biochemical structures or compounds with great therapeutic potential for patients with heart disease.

Derivation of stromal (skeletal and mesenchymal) stem-like cells from human embryonic stem cells

Derivation of bone forming cells (osteoblasts) from human embryonic stem cells (hESCs) is a prerequisite for their use in clinical applications. However, there is no standard protocol for differentiating hESCs into osteoblastic cells. The aim of this study was to identify the emergence of a human stromal (mesenchymal and skeletal) stem cell (hMSC)-like population, known to be osteoblastic cell precursors and to test their osteoblastic differentiation capacity in ex vivo cultures and in vivo. We cultured hESCs in a feeder-free environment using serum replacement and as suspension aggregates (embryoid bodies; hEBs). Over a 20 day developmental period, the hEBs demonstrated increasing enrichment for cells expressing hMSC markers: CD29, CD44, CD63, CD56, CD71, CD73, CD105, CD106, and CD166 as revealed by immunohistochemical staining and flow cytometry (fluorescence-activated cell sorting) analysis. Ex vivo differentiation of hEBs using bone morphogenic protein 2 (BMP2) combined with standard osteoblast induction medium led to weak osteoblastic induction. Conversely, subcutaneous in vivo implantation of day 20 hEBs in immune deficient mice, mixed with hydroxyapatite/tricalcium phosphate (HA/TCP) as an osteoconductive scaffold, revealed bone and cartilage, and fibrous tissue elements after 8 weeks. These tissues were of human origin and there was no evidence of differentiation to nonmesodermal tissues. hEBs implanted in the absence of HA/TCP formed vacuolated tissue containing glandular, fibrous and muscle-like tissue elements. Conversely, implantation of undifferentiated hESCs resulted in the formation of a teratoma containing a mixture of endodermal, mesodermal, and ectodermal tissues. Our study demonstrates that hMSC-like cells can be obtained from hESCs and they can be induced to form skeletal tissues in vivo when combined with HA/TCP. These findings are relevant for tissue engineering and suggest that differentiated hEBs can provide an unlimited source for functional osteogenic cells.

Gene expression changes in C57BL/6J and DBA/2J mice following prenatal alcohol exposure

BACKGROUND

Prenatal alcohol exposure can result in fetal alcohol spectrum disorders (FASD). Not all women who consume alcohol during pregnancy have children with FASD and studies have shown that genetic factors can play a role in ethanol teratogenesis. We examined gene expression in embryos and placentae from C57BL/6J (B6) and DBA/2J (D2) mice following prenatal alcohol exposure. B6 fetuses are susceptible to morphological malformations following prenatal alcohol exposure while D2 are relatively resistant.

METHODS

Male and female B6 and D2 mice were mated for 2 hours in the morning, producing 4 embryonic genotypes: true-bred B6B6 and D2D2, and reciprocal B6D2 and D2B6. On gestational day 9, dams were intubated with 5.8 g/kg ethanol, an isocaloric amount of maltose dextrin, or nothing. Four hours later, dams were sacrificed and embryos and placentae were harvested. RNA was extracted, labeled and hybridized to Affymetrix Mouse Genome 430 v2 microarray chips. Data were normalized, subjected to analysis of variance and tested for enrichment of gene ontology molecular function and biological process using the Database for Annotation, Visualization and Integrated Discovery (DAVID).

RESULTS

Several gene classes were differentially expressed in B6 and D2 regardless of treatment, including genes involved in polysaccharide binding and mitosis. Prenatal alcohol exposure altered expression of a subset of genes, including genes involved in methylation, chromatin remodeling, protein synthesis, and mRNA splicing. Very few genes were differentially expressed between maltose-exposed tissues and tissues that received nothing, so we combined these groups for comparisons with ethanol. While we observed many expression changes specific to B6 following prenatal alcohol exposure, none were specific for D2. Gene classes up- or down-regulated in B6 following prenatal alcohol exposure included genes involved in mRNA splicing, transcription, and translation.

CONCLUSIONS

Our study identified several classes of genes with altered expression following prenatal alcohol exposure, including many specific for B6, a strain susceptible to ethanol teratogenesis. Lack of strain specific effects in D2 suggests there are few gene expression changes that confer resistance. Future studies will begin to analyze functional significance of the expression changes.

Quantitative trait locus mapping for ethanol teratogenesis in BXD recombinant inbred mice

BACKGROUND

Individual differences in susceptibility to the detrimental effects of prenatal ethanol (EtOH) exposure have been demonstrated. Many factors, including genetics, play a role in susceptibility and resistance. We have previously shown that C57BL/6J (B6) mice display a number of morphological malformations following an acute dose of EtOH in utero, while DBA/2J (D2) mice are relatively resistant. Here, we present the results of quantitative trait locus (QTL) mapping for EtOH teratogenesis in recombinant inbred strains derived from a cross between B6 and D2 (BXD RIs).

METHODS

Pregnant dams were intubated with either maltose-dextrin or 5.8 g/kg EtOH on day 9 of gestation (GD9). On GD 18, dams were sacrificed and fetuses and placentae were removed. Placentae and fetuses were weighed; fetuses were sexed and examined for gross morphological malformations. Fetuses were then either placed in Bouin's fixative for subsequent soft-tissue analyses or eviscerated and placed in EtOH for subsequent skeletal examinations. QTL mapping for maternal weight gain (MWG), prenatal mortality, fetal weight (FW) at c-section, placental weight (PW), and several morphological malformations was performed using WebQTL.

RESULTS

Heritability for our traits ranged from 0.06 for PW to 0.39 for MWG. We found suggestive QTLs mediating all phenotypes and significant QTLs for FW and digit and rib malformations. While most QTL regions are large, several intriguing candidate genes emerged based on polymorphisms between B6 and D2 and gene function.

CONCLUSIONS

In this first mapping study for EtOH teratogenesis, several QTLs were identified. Future studies will further characterize these regions. Identification of genes and epigenetic modifications mediating susceptibility to the teratogenic effects of alcohol in mice will provide targets to examine in human populations.

The response of annulus fibrosus cell to fibronectin-coated nanofibrous polyurethane-anionic dihydroxyoligomer scaffolds

Tissue engineering of the annulus fibrosus(AF), a component of the intervertebral disc, has proven to be challenging due to its complex oriented lamellar structure. Previously it was demonstrated that polyurethane (PU) scaffolds containing an anionic dihydroxy oligomers (ADO) may be suitable to use in this application. The current study examines whether matrix protein(s) coatings (collagen type I, collagen type I and fibronectin, fibronectin, or vitronectin) would promote cell and collagen orientation that more closely mimics native AF. The greatest cell attachment occurred when scaffolds were pre-coated with Fn. Cells on Fn-coated scaffolds were aligned parallel to scaffold fibers, a process that involved α5β1 integrin, as determined by integrin-specific blocking antibodies, which in turn reduced AF cell spreading and alignment. Cell shape was regulated by the actin cytoskeleton as cells grown in the presence of cytochalasin D did not spread. Cells on Fn-coated PU scaffolds formed fibrillar Fn, synthesized significantly more collagen, and showed linear alignment of the secreted type I collagen when compared to cells grown on the other protein-coated scaffolds and the non-coated control. Thus Fn-coating of PU-ADO scaffolds appears to promote properly oriented AF cells and collagen, which should facilitate developing AF tissue that more closely mimics the native tissue.

Involvement of the MEKK1 signaling pathway in the regulation of epicardial cell behavior by hyaluronan

During embryonic development, cells comprising the outermost layer of the heart or epicardium play a critical role in the formation of the coronary vasculature. Thus, uncovering the molecular mechanisms that govern epicardial cell behavior is imperative to better understand the etiology of cardiovascular diseases. In this study, we investigated the function of hyaluronan (HA), a major component of the extracellular matrix, in the modulation of epicardial signaling. We show that stimulation of epicardial cells with high molecular weight HA (HMW-HA) promotes the association of MEKK1 with the HA receptor CD44 and induces MEKK1 phosphorylation. This leads to the activation of two distinct pathways, one ERK-dependent and another NFkappaB-dependent. Furthermore, HMW-HA stimulates epicardial cells to differentiate and invade, as suggested by increased vimentin expression and enhanced invasion through a collagen matrix. Blockade of CD44, transfection with a kinase-inactive MEKK1 construct or the use of ERK1/2 and NFkappaB inhibitors significantly abrogates the invasive response to HMW-HA. Together, these findings suggest an important role for HA in the regulation of epicardial cell fate via activation of MEKK1 signaling cascades.

An obligatory role of mind bomb-1 in notch signaling of mammalian development

BACKGROUND

The Notch signaling pathway is an evolutionarily conserved intercellular signaling module essential for cell fate specification that requires endocytosis of Notch ligands. Structurally distinct E3 ubiquitin ligases, Neuralized (Neur) and Mind bomb (Mib), cooperatively regulate the endocytosis of Notch ligands in Drosophila. However, the respective roles of the mammalian E3 ubiquitin ligases, Neur1, Neur2, Mib1, and Mib2, in mammalian development are poorly understood.

METHODOLOGY/PRINCIPAL FINDINGS

Through extensive use of mammalian genetics, here we show that Neur1 and Neur2 double mutants and Mib2(-/-) mice were viable and grossly normal. In contrast, conditional inactivation of Mib1 in various tissues revealed the representative Notch phenotypes: defects of arterial specification as deltalike4 mutants, abnormal cerebellum and skin development as jagged1 conditional mutants, and syndactylism as jagged2 mutants.

CONCLUSIONS/SIGNIFICANCE

Our data provide the first evidence that Mib1 is essential for Jagged as well as Deltalike ligand-mediated Notch signaling in mammalian development, while Neur1, Neur2, and Mib2 are dispensable.

The role of CD44 splice variants in human metastatic cancer

The large family of CD44 splice variants are likely to serve multiple functions in the embryo and in the adult organism. This is reflected in their complex patterns of expression. In molecular terms these functions are largely unknown. Certain splice variants (CD44v) can promote the metastatic behaviour of cancer cells. In human colon and breast cancer the presence of epitopes encoded by exon v6 on primary resected tumour material indicates poor prognosis. Metastasis-promoting splice variants differ from those that seem not to have a role in the induction of metastasis by the formation of homomultimeric complexes in the plasma membrane of cells. This may increase their affinity to ligands such as hyaluronate. The affinity can be further regulated over a range from low to very high by cell-specific modification. The fact that CD44v epitopes are found on normal epithelial cells such as skin, cervical epithelium and bladder enforces cautious evaluation of the significance of CD44v expression in human cancer. Nevertheless, certain epitopes can serve as tools in early diagnosis of certain cancers and will facilitate the development of specific targeted therapy.

Effect of glycosaminoglycans on the preimplantation development of embryos derived from in vitro fertilization and somatic cell nuclear transfer

The purpose of this study was to evaluate the effect of glycosaminoglycans (GAGs) added to the culture medium on the developmental competence of bovine embryos derived from in vitro fertilization (IVF) and from somatic cell nuclear transfer (SCNT). In vitro-matured oocytes were either inseminated with 1 x 10(6) spermatozoa mL(-1) or enucleated and reconstructed with bovine adult ear fibroblasts by SCNT. The embryos were then cultured in modified synthetic oviduct fluid (mSOF) containing 8 mg mL(-1) bovine serum albumin (BSA) (control mSOF) or control mSOF supplemented with various GAGs (hyaluronic acid, heparin or chondroitin sulfate) in a dose-dependent manner (0.1, 0.5 or 1.0 mg mL(-1)). Developmental competence was evaluated by monitoring the numbers of 2-cell embryos, 8-16-cell embryos and blastocysts. The mean cell number of flattened blastocysts stained with 5 microM bisbenzimide on Day 8 was counted. The percentage of blastocyst formation (IVF and SCNT embryos) from cleaved embryos was significantly higher (P < 0.05) in control mSOF supplemented with 0.5 mg mL(-1) hyaluronic acid (45% and 47%), heparin (40% and 47%) or chondroitin sulfate (38% and 44%) compared with control mSOF (30-31% and 30-33%). When compared with the efficacy of 0.5 mg mL(-1) GAGs, no significant differences were observed in the developmental competence of both IVF and SCNT embryos. Supplementing control mSOF with 0.5 mg mL(-1) GAGs had no effect on the cell number of IVF embryos. In contrast, supplementing 0.5 mg mL(-1) of hyaluronic acid, heparin or chondroitin sulfate to control mSOF significantly (P < 0.05) increased the numbers of total cells (93-98 v. 88 cells) and trophectoderm (TE) cells (64-66 v. 55 cells), and decreased the inner cell mass (ICM) to TE cell ratio (48.2-49.8 v. 61.3) in SCNT blastocysts compared with embryos in control mSOF. In conclusion, supplementation of culture media with GAGs may improve the development of bovine IVM-IVF and SCNT embryos to the blastocyst stage. The GAGs increased the quality of blastocysts by increasing total cell numbers in the SCNT embryos.

Temporal variation in the distribution of hyaluronic acid, CD44s, and CD44v6 in the human endometrium across the menstrual cycle

Tissues undergoing rapid growth and regeneration contain hyaluronic acid (HA) as a prominent component of the extracellular matrix. The physiologic role of HA is partly mediated by its relationship with CD44, its major cell surface receptor. Given the extensive remodeling of the endometrium during the menstrual cycle, the authors sought to determine whether these changes are related to the levels of HA, CD44s, and CD44v6 in the endometrium. Archival paraffin embedded cell blocks from 10 cases of proliferative endometrium and 20 cases of secretory endometrium were retrieved from the surgical pathology files. Specimens from the secretory phase were subdivided into three categories: early secretory (day 15-18), mid-secretory (day 19-23), and late secretory (day 24-28). All cases were stained for hyaluronic acid, CD44s, and CD44v6. Sections from umbilical cord, tonsil, and squamous cell carcinoma served as positive controls for HA, CD44s, and CD44v6, respectively. Positive staining was defined as droplet to diffuse intracytoplasmic or extracellular staining for HA and uniform membranous staining for CD44. During the proliferative phase, the endometrial glands and the stroma were both negative for CD44s and CD44v6 in all cases. In the secretory phase, the endometrial glands were negative for CD44s in all cases, but CD44v6 was expressed in 12 (60%) of cases. In contrast, the stromal cells expressed CD44s in 18 (90%) cases and were negative for CD44v6 in all cases. HA staining was present in the endometrial stroma throughout the menstrual cycle but was most intense (3+) and diffuse during the midsecretory phase. There was perivascular staining for HA throughout the cycle; it was most intense adjacent to the spiral arterioles in the secretory phase. These data indicate temporal and geographic differences in HA and CD44 staining in the endometrium in concert with the menstrual cycle. The timing of peak staining of HA and CD44s in the stroma and the upregulation of CD44v6 in secretory glands are coincident with the period in which the endometrium is most receptive to embryo implantation. Whether these changes are mere hormonal consequences or actually help modulate the cyclical changes in the endometrium warrants further study.

Embryonic and adult stem cell-derived cardiomyocytes: lessons from in vitro models

For years, research has focused on how to treat heart failure by sustaining the overloaded remaining cardiomyocytes. Recently, the concept of cell replacement therapy as a treatment of heart diseases has opened a new area of investigation. In vitro-generated cardiomyocytes could be injected into the heart to rescue the function of a damaged myocardium. Embryonic and/or adult stem cells could provide cardiac cells for this purpose. Knowledge of fundamental cardiac differentiation mechanisms unraveled by studies on animal models has been improved using in vitro models of cardiogenesis such as mouse embryonal carcinoma cells, mouse embryonic stem cells and, recently, human embryonic stem cells. On the other hand, studies suggesting the existence of cardiac stem cells and the potential of adult stem cells from bone marrow or skeletal muscle to differentiate toward unexpected phenotypes raise hope and questions about their potential use for cardiac cell therapy. In this review, we compare the specificities of embryonic vs adult stem cell populations regarding their cardiac differentiation potential, and we give an overview of what in vitro models have taught us about cardiogenesis.

Exogenous hyaluronic acid enhances porcine parthenogenetic embryo development in vitro possibly mediated by CD44

Exogenous hyaluronic acid (HA) has been reported to improve early embryo development in vitro in pigs and cows. Although early embryo development in vitro is improved by exogenous HA, the mechanism mediating the action of HA is not clearly defined. In the present study, two possible HA actions on early embryo development were proposed to understand interactions between HA and the embryos using porcine parthenotes. We hypothesized that improvement of early embryo development mediated by HA would be caused by embryo-derived growth factors due to the high molecular weight of HA or cellular response through its receptor (CD44). We examined the effects of HA molecular weight on parthenogenetic embryo development, permeability of HA into the zona pellucida, expression of CD44 in porcine parthenotes at various stages, and blocking interactions between HA and CD44 by monoclonal anti-CD44 antibody (mCD44Ab). As a result, although development of porcine parthenotes to the blastocyst stage was significantly enhanced by exogenous HA with various molecular weights, there was no difference in blastocyst formation among the various molecular weights (P < 0.05). Immunofluorescence revealed that exogenous HA was accessible to CD44 through the zona pellucida, irrespective of the oocyte activation and that CD44 was also expressed in both oocytes and parthenotes at all developmental stages. In addition, development of parthenotes was partially blocked by mCD44Ab. In conclusion, we demonstrated that exogenous HA enhanced development of porcine parthenotes in vitro. This improvement mediated by exogenous HA on parthenogenetic embryo development was possibly caused by cellular response via CD44.

Expression of the CD44 Receptor in the Blood Vessel System: An Experimental Study in Rat

The CD44 receptor is a transmembrane glycoprotein expressed on a variety of cells like endothelial, epithelial and smooth muscle cells. This molecule has many important functions, e.g. in cell-cell and cell-matrix interactions and signal transduction. The main ligand for CD44 is hyaluronan (HYA). HYA is a glycosaminoglycan with structural and cell biological properties. The localization of HYA in the vessel wall of arteries and veins in the healthy adult and newborn rat has been described earlier. In this study the occurrence of the CD44 receptor was investigated in the same vessels and compared to the localization of HYA. Both CD44 and its ligand showed an increased expression in the vessel wall of newborn rats compared to that of adult rats. Although HYA is abundant in the adventitia of adult rats, virtually no expression of CD44 was observed. Our results indicate that the CD44 receptor expression is increased during the stage of maturation of the vessel tree whereas the CD44 receptor is less needed by HYA in the healthy vessel wall.

Embryotropic effect of glycosaminoglycans and receptors in development of porcine pre-implantation embryos

The present study investigated the expression of receptors for glycosaminoglycans (GAGs) and the effect of GAGs supplementation on development of porcine IVF embryos. Total RNA was prepared from oocytes, 2-, 4- and 8-cell embryos, morulae and blastocysts. The expression of hyaluronic acid receptor (CD44) and heparin (HP) interacting protein (HIP) was determined using RT-PCR and Southern blot analysis. The CD44 and HIP mRNA were detected from in vitro matured oocytes and all stages of pre-implantation embryos. The IVF embryos were cultured in modified NCSU-23 medium supplemented with various concentrations (0, 0.1, 0.5 or 1.0 mg/mL) of hyaluronic acid (HA) or heparin. Supplementing with 0.5 mg/mL HA significantly increased total cell number compared to other experimental groups, due to increase in trophectoderm cells. Supplementing with 1.0 mg/mL, HP significantly increased blastocyst formation rate compared to the control group. Supplementing media, in which IVF embryos were cultured with 0.5 mg/mL HA + 1.0 mg/mL HP, significantly increased blastocyst formation rate compared to the control group. In conclusion, the present study demonstrated the expression of HA and HP receptors and the embryotrophic effect of HA or HP on porcine IVF embryos.

Haploinsufficient lethality and formation of arteriovenous malformations in Notch pathway mutants

The Notch signaling pathway is essential for embryonic vascular development in vertebrates. Here we show that mouse embryos heterozygous for a targeted mutation in the gene encoding the DLL4 ligand exhibit haploinsufficient lethality because of defects in vascular remodeling. We also describe vascular defects in embryos homozygous for a mutation in the Rbpsuh gene, which encodes the primary transcriptional mediator of Notch signaling. Conditional inactivation of Rpbsuh function demonstrates that Notch activation is essential in the endothelial cell lineage. Notch pathway mutant embryos exhibit defects in arterial specification of nascent blood vessels and develop arteriovenous malformations. These results demonstrate that vascular remodeling in the mouse embryo is sensitive to Dll4 gene dosage and that Notch activation in endothelial cells is essential for embryonic vascular remodeling.

CD44 variant isoforms associate with tetraspanins and EpCAM

The metastasizing subline of the rat pancreatic adenocarcinoma BSp73 expresses a set of membrane molecules, the combination of which has not been detected on non-metastasizing tumor lines. Hence, it became of interest whether these molecules function independently or may associate and exert specialized functions as membrane complexes. Separation of CD44v4-v7 containing membrane complexes in mild detergent revealed an association with the alpha3 integrin, annexin I, EpCAM, and the tetraspanins D6.1A and CD9. EpCAM and the tetraspanins associate selectively with CD44 variant (CD44v), but not with the CD44 standard (CD44s) isoform. The complexes are found in glycolipid-enriched membrane (GEM) microdomains, which are dissolved by stringent detergents, but the complexes are not destroyed by methyl-beta-cyclodextrin (MbetaCD) treatment, which implies that complex formation does not depend on a lipid-rich microenvironment. However, a complex-associated impact on cell-matrix and cell-cell adhesion as well as on resistance towards apoptosis essentially depended on the location in GEMs. Thus, CD44v-specific functions may well be brought about by complex formation of CD44v with EpCAM, the tetraspanins, and the alpha3 integrin. Because CD44v4-v7-EpCAM complex-specific functions strictly depended on the GEM localization, linker or signal-transducing molecules associating with the complex are likely located in GEMs.

Butyric and retinoic mixed ester of hyaluronan. A novel differentiating glycoconjugate affording a high throughput of cardiogenesis in embryonic stem cells

Embryonic stem (ES) cells can differentiate into specialized cells, including cardiac myocytes, but the efficiency is typically low and the process is incompletely understood. Achieving a high throughput of cardiogenesis from pluripotent cells is therefore a major requirement for future approaches in cardiac cell therapy. Here, we developed a novel ester of hyaluronan linked to both butyric and retinoic acid (HBR), coaxing pluripotent ES cells into a cardiogenic decision. In mouse ES cells, HBR remarkably increased the expression of GATA-4 and Nkx-2.5, acting as cardiac lineage-promoting genes in different animal species, including humans. HBR also enhanced prodynorphin gene expression and the synthesis and secretion of dynorphin B, an endorphin playing a major role in ES cell cardiogenesis. These effects occurred at the transcriptional level. HBR also primed the expression of cardiac-specific transcripts and highly enhanced the yield of spontaneously beating ES-derived cardiomyocytes. These results demonstrate the potential for chemically modifying the gene program of cardiac differentiation in ES cells without the aid of gene transfer technologies and may pave the way for novel approaches in tissue engineering and myocardial regeneration.

The Notch target genes Hey1 and Hey2 are required for embryonic vascular development

The Delta-Notch signaling pathway plays a central role in the development of most vertebrate organs. The Hey family of bHLH transcription factors are direct targets of Notch signaling. Loss of Hey2 in the mouse leads to cardiac defects with high postnatal lethality. We have now generated a mouse Hey1 knockout that has no apparent phenotypic defect. The combined loss of Hey1 and Hey2, however, results in embryonic death after embryonic day 9.5 (E9.5) with a global lack of vascular remodeling and massive hemorrhage. Initial vasculogenesis appears unaffected, but all subsequently developing major vessels in the embryo and yolk sac are either small or absent. Furthermore, the placental labyrinth completely lacks embryonic blood vessels. Similar vascular defects are observed in Jagged1 and Notch1 knockout mice. In the latter we found Hey1 and Hey2 expression in yolk sacs to be strongly reduced. Remaining large arteries in both Notch1 and Hey1/Hey2 knockout mice fail to express the arterial endothelial markers CD44, neuropilin1, and ephrin-B2. This indicates that Hey1/Hey2 are essential transducers of Notch signals in cardiovascular development that may mediate arterial cell fate decision.

Inflammatory cytokines can enhance CD44-mediated airway epithelial cell adhesion independently of CD44 expression

In airways, the cell surface molecule CD44 is upregulated on bronchial epithelial cells in areas of damage. We have shown that a blocking standard CD44 (CD44s) antibody caused a 77% (+/- 19%) inhibition of cell migration at 3 h after mechanical damage and decreased epithelial cell repair of cells grown on cell culture filter inserts. With the use of primary human bronchial epithelial cells and the bronchial epithelial cell line 16HBE 14o-, a CD44s antibody inhibited >95% (P < 0.01) of cell binding to hyaluronic acid (HA). The cytokines TNF-alpha, IFN-gamma, IL-1 beta, and IL-4 stimulated a 2- to 3.5-fold increase in CD44-dependent cell binding to HA. IFN-gamma treatment did not increase CD44 expression as assessed by flow cytometry, although phorbol myristate acetate treatment did. This indicates that IFN-gamma-induced cell binding to HA did not require increased CD44 expression. These data indicate that CD44 is important for bronchial epithelial cell binding to HA and that cytokines known to be expressed in inflammation can increase HA binding independently of the level of CD44 expression.

The hyaluronic acid receptor (CD44) is expressed in bovine oocytes and early stage embryos

Hyaluronic acid (HA) is a high molecular weight polysaccharide found in the extracellular matrix of most animal tissues, that exerts a profound influence on cell behavior. HA is one of the most abundant glycosaminoglycans (GAGs) in the uterine, oviductal and follicular fluids in mouse, pig, human and cattle. CD44, the principal cell membrane receptor for HA, is expressed from the 1- to 8-cell stage in human embryos, during post-implantation mouse embryogenesis and on the surface of differentiated embryonic stem cells. In the present study, we have analyzed by immunofluorescence, whether CD44 is present in bovine oocytes, fertilized oocytes and early stage embryos. Bovine cumulus-oocyte complexes (COCs) were aspirated from follicles (2-5mm) and were selected for IVM and incubated for 24h. Oocytes showing an expanded cumulus (generally 90-95%) were used for IVF. Fertilized oocytes were separated for immunofluorescence assay after 16h of sperm incubation in order to fix the eggs at the pronuclear stage. The embryos were cultured for 8 days and the different stages of development for immunofluorescence assay were separated every 24h of culture. The CD44 receptor was detected at every observation time examined. Fluorescence-tagged HA for the internalization assay was prepared by mixing fluorescein amine, Isomer I and 1mg of HA from umbilical cord. Fluorescence-tagged HA was internalized in 2-, 4-, 8- and 16-cell-stage embryos, morulae and blastocysts. CD44 is expressed on the surface and in the cytoplasm of bovine oocytes and embryos in different stages of development.

Hyaluronan and CD44: strategic players for cell-matrix interactions during chondrogenesis and matrix assembly

Embryonic induction, soluble and insoluble factors, receptors, and signal transduction are orchestrated for the morphogenesis of the cartilage elements. The interaction of cells with the extracellular matrix (ECM) may lead to altered cellular response to morphogens based on the formation of new adhesive contacts, or the uncoupling of cell-matrix interactions. Hyaluronan's influence on cell behavior, and its intimate association with cells are accomplished by a wide variety of specific binding proteins for hyaluronan. The temporal expression of the hyaluronan receptor CD44 (which is expressed as several alternatively spliced variants) may be strategic to many of these cell-matrix interactions during chondrogenesis. CD44 expression is temporally coincident with the reduction of intercellular spaces at the regions of future cartilage deposition. The spatial organization of CD44 at the cell surface may function to establish or regulate the structure of the pericellular matrix dependent on a hyaluronan scaffold. As the ECM is modified during embryogenesis, the cellular response to inductive signals may be altered. An uncoupling of chondrocyte-hyaluronan interaction leads to chondrocytic chondrolysis. Thus, consideration of cell-matrix interactions during chondrogenesis, in the light of our current understanding of the temporal and spatial expression of signaling morphogens, should become a promising focus of future research endeavors.

Cell-matrix interactions of in vitro human skin fibroblasts upon addition of hyaluronan

Normal human skin fibroblasts were grown in a three-dimensional collagen gel or in monolayer in the presence or absence of high molecular weight hyaluronan (HA) to assess the influence of extracellular HA on cell-matrix interactions. HA incorporated into the collagen gel or added to the culture medium did not modify lattice retraction with time. The effect was independent from HA molecular weight (from 7.5 x 10(5) to 2.7 x 10(6) Da) and concentration (from 0.1 up to 1 mg/ml). HA did not affect shape and distribution of fibroblasts within the gel, whereas it induced the actin filaments to organise into thicker cables running underneath the plasma membrane. The same phenomenon was observed in fibroblasts grown in monolayer. By contrast, vimentin cytoskeleton and cell-substrate focal adhesions were not modified by exogenous HA. The number of fibroblasts attached to HA-coated dishes was always significantly lower compared to plastic and to collagen type I-coated plates. By contrast, adhesion was not affected by soluble HA added to the medium nor by anti-CD44 and anti-RHAMM-IHABP polyclonals. After 24-h seeding on collagen type I or on plastic, cells were large and spread. Conversely, cells adherent to HA-coated surfaces were long, thin and aligned into rows; alcian blue showed that cells were attached to the plastic in between HA bundles. Therefore, normal human skin fibroblasts exhibit very scarce, if any, adhesion to matrix HA, either soluble or immobilised. Moreover, even at high concentration, HA molecules do not exert any visco-mechanical effect on lattice retraction and do not interfere with fibroblast-collagen interactions nor with focal adhesion contacts of fibroblasts with the substrate. This is probably relevant in organogenesis and wound repair. By contrast, HA greatly modifies the organisation of the actin cytoskeleton, suggesting that CD44-mediated signal transduction by HA may affect cell locomotion and orientation, as indicated by the fusiform shape of fibroblasts grown in the presence of immobilised HA. A role of HA in cell orientation could be relevant for the deposition of collagen fibrils in regeneration and tissue remodelling.

Blocking endogenous FGF-2 activity prevents cranial osteogenesis

Normal growth and morphogenesis of the cranial vault reflect a balance between cell proliferation in the sutures and osteogenesis at the margins of the cranial bones. In the clinical condition craniosynostosis, the sutures fuse prematurely as a result of precocious osteogenic differentiation and craniofacial malformation results. Mutations in several fibroblast growth factor receptor (FGFR) genes have now been identified as being responsible for the major craniosynostotic syndromes. We have used a grafting technique to manipulate the levels of endogenous FGF-2 ligand in embryonic chick cranial vaults and thereby perturb morphogenesis. Implantation of beads loaded with FGF-2 did not affect normal cranial development at physiological concentrations, although they elicited a morphogenetic response in the limb. Implantation of beads loaded with a neutralising antibody to FGF-2 generated a concentration-dependent response. When a single bead was implanted, the grafts grew to a massive size as a result of increased cell division in the tissue. With greater inactivation of FGF-2 protein (two to three beads implanted), all further bone differentiation and cell proliferation was blocked. These data further support the emerging idea that the intensity of FGF-mediated signalling determines the developmental fate of the skeletogenic cells in the cranial vault. High and low levels correlate with differentiation and proliferation, respectively. A balance between the two ensures normal cranial vault morphogenesis. This is consistent with the observation that several FGFR mutations causing craniosynostosis result in constitutive activation of the receptor.

Temporal expression of CD44 during embryonic chick limb development and modulation of its expression with retinoic acid

Hyaluronan-cell interactions are initiated co-ordinately with mesenchymal condensation during chondrogenic differentiation in the limb bud. Hyaluronan is responsible for the retention and organization of proteoglycan within the cartilage matrix. Hyaluronan-CD44 binding also retains proteoglycan aggregates to the chondrocyte plasma membrane. A sequence for CD44 protein in chick has recently been reported, but never evaluated in chick chondrocytes. Total RNA was isolated from embryonic chick limb buds, stages 18, 19, 24, 25 and 30. Using semi-quantitative RT-PCR, expression of aggrecan, this chick CD44 orthologue and GAPDH mRNA was analyzed. Aggrecan expression was detected at all stages, but was increased at stage 30. CD44 mRNA was detected at extremely low levels at stage 18 to higher levels in the latter stages. Thus, the temporal expression of CD44 mRNA correlated with the onset of pre-cartilage condensation. The full-length chick chondrocyte CD44 cDNA was obtained following RT-PCR using RNA derived from tibial chondrocytes from stage 37 chick embryos. The nucleotide sequence was used to generate an amino acid sequence and analyses revealed homologies of 44.4% with mouse, 47.8% with bovine and 46.3% with human CD44. Tibial chondrocytes were cultured in the presence or absence of retinoic acid for 36 or 72 h. By RT-PCR, expression of aggrecan and the CD44 mRNA by chick chondrocytes was decreased after retinoic acid treatment, while GAPDH expression showed no change. As expected, control chondrocytes exhibited a round morphology while retinoic acid-treated chondrocytes were elongated. The retinoic acid-treated chondrocytes also exhibited reduced hyaluronan binding. This functional assay indicates a role for a CD44 receptor in matrix retention by chick chondrocytes.

Increased resistance to collagen-induced arthritis in CD44-deficient DBA/1 mice

OBJECTIVE

To study the role of CD44, the principal hyaluronan (HA) receptor, in experimental arthritis.

METHODS

We generated CD44 gene deficiency in arthritis-susceptible DBA/1LacJ mice to study the role of CD44 directly in collagen-induced arthritis (CIA). Wild-type and CD44-deficient mice were immunized with chicken type II collagen, and the onset and severity of CIA were monitored up to day 64. The immune status of immunized mice was determined at the end of the experiments. Cell transfer experiments were performed to monitor lymphocyte traffic to the inflamed joints.

RESULTS

Mice homozygous for the CD44 mutation developed normally and showed no phenotypic defects. Although they showed a normal response to immunization with type II collagen and had Th1/Th2 ratios comparable with those in wild-type animals, CD44-deficient mice exhibited significant reductions in both the incidence and severity of CIA. This was accompanied by altered serum levels of HA, reduced expression of L-selectin, and a delayed entry of intravenously injected CD44-deficient donor lymphocytes into the arthritic joints of recipient mice.

CONCLUSION

While CD44 is not essential for morphogenesis and autoimmunity, this cell surface receptor seems to play an important role in the development of arthritis, most likely by directing leukocyte traffic to the site of inflammation.

Mice null for sox18 are viable and display a mild coat defect

We have previously shown that Sox18 is expressed in developing vascular endothelium and hair follicles during mouse embryogenesis and that point mutations in Sox18 are the underlying cause of cardiovascular and hair follicle defects in ragged (Ra) mice. Here we describe the analysis of Sox18(-/-) mice produced by gene targeting. Despite the profound defects seen in Ra mice, Sox18(-/-) mice have no obvious cardiovascular defects and only a mild coat defect with a reduced proportion of zigzag hairs. A reduction in the amount of pheomelanin pigmentation in hair shafts was also observed; later-forming hair follicles showed a reduced subapical pheomelanin band, giving Sox18(-/-) mice a slightly darker appearance than Sox18(+/+) and Sox18(+/-) siblings. Sox18(-/-) mice are viable and fertile and show no difference in the ability to thrive relative to littermates. Because of the mild effect of the mutation on the phenotype of Sox18(-/-) mice, we conclude that the semidominant nature of the Ra mutations is due to a trans-dominant negative effect mediated by the mutant SOX18 proteins rather than haploinsufficiency as has been observed for other SOX genes. Due to the similarity of SOX18 to other subgroup F SOX proteins, SOX7 and -17, and the overlap in expression of these genes, functional redundancy amongst these SOX proteins could also account for the mild phenotype of Sox18(-/-) mice.

Increased CD44 expression in human bronchial epithelial repair after damage or plating at low cell densities

We have investigated the effect of mechanical damage, cell density, and cell-derived soluble mediators on CD44 expression in a model of bronchial epithelial repair. CD44 (all isoforms) and variant-containing isoforms (CD44v3, CD44v6, and CD44v9) were identified with flow cytometry and immunocytochemistry with image analysis. After mechanical damage, CD44 expression increased up to 500 microm from the wound edge and for up to 48 h in two human bronchial epithelium-derived cell lines, 16HBE14o- and NCI-H292. CD44 expression was unchanged by interferon-gamma and increased by <50% by tumor necrosis factor-alpha. To exclude other soluble factors, a Vaseline spacer was used to temporarily divide petri dishes, with cells at high density on one side and those at low density on the other. After the spacer was removed, the cells at low cell density growing in the shared medium expressed up to fourfold higher CD44, although cell proliferation was unchanged. Thus increased CD44 expression at low cell density was not mediated by soluble factors and may reflect functional involvement in cell motility, dedifferentiation, or altered cell-substrate adhesion in epithelial repair.

Ras, protein kinase C zeta, and I kappa B kinases 1 and 2 are downstream effectors of CD44 during the activation of NF-kappa B by hyaluronic acid fragments in T-24 carcinoma cells

We have investigated the ability of hyaluronic acid (HA) fragments to activate the transcription factor NF-kappa B. HA fragments activated NF-kappa B in the cell lines T-24, HeLa, MCF7, and J774. Further studies in T-24 cells demonstrated that HA fragments also induced I kappa B alpha phosphorylation and degradation, kappa B-linked reporter gene expression, and ICAM-1 promoter activity in an NF-kappa B-dependent manner. The effect of HA was size dependent as neither disaccharide nor native HA were active. CD44, the principal cellular receptor for HA, was critical for the response because the anti-CD44 Ab IM7.8.1 blocked the effect on NF-kappa B. HA fragments activated the I kappa B kinase complex, and the effect on a kappa B-linked reporter gene was blocked in T-24 cells expressing dominant negative I kappa B kinases 1 or 2. Activation of protein kinase C (PKC) was required because calphostin C inhibited NF-kappa B activation and I kappa B alpha phosphorylation. In particular, PKC zeta was required because transfection of cells with dominant negative PKC zeta blocked the effect of HA fragments on kappa B-linked gene expression and HA fragments increased PKC zeta activity. Furthermore, damnacanthal and manumycin A, two mechanistically distinct inhibitors of Ras, blocked NF-kappa B activation. Transfection of T-24 cells with dominant negative Ras (RasN17) blocked HA fragment-induced kappa B-linked reporter gene expression, and HA fragments activated Ras activity within 5 min. Taken together, these studies establish a novel signal transduction cascade emanating from CD44 to Ras, PKC zeta, and I kappa B kinase 1 and 2.

CD44 expression in benign, premalignant, and malignant ovarian neoplasms: relation to tumour development and progression

To clarify the possible role of CD44 expression in ovarian tumour development and progression, an immunohistochemical investigation was undertaken of a series of 115 carcinomas, 32 tumours with low malignant potential (LMP), and 53 cystadenomas. A combination of the reverse transcription-polymerase chain reaction (RT-PCR) and Southern blot hybridization (SBH) assays was also performed for 17 malignant, four LMP, six cystadenoma, and seven normal ovarian samples. Immunoreactivity scores for CD44s, CD44v3, and CD44v6 were significantly higher in LMP and malignant tumours than in the benign or normal cases, in line with the results of gross mRNA-based assays. Exon-specific RT-PCR/SBH assays revealed that the expression of large CD44 transcripts containing v6 to v8 exons and small isoforms containing v2 and v3 was common among normal and neoplastic tissues, while a simultaneous increase of large isoforms containing v2 to v5 was also revealed in LMP and malignant tumours. In ovarian carcinomas, the scores for CD44s, CD44v3, and CD44v6 were inversely related to the FIGO stage, but there was no association with lymph node status or expression of hormone receptors. Multivariate analysis revealed loss of CD44v3 expression to be an independent factor for poor survival. The findings indicate that CD44 is up-regulated during the development of ovarian carcinomas but is subsequently down-regulated during their progression, resulting in aggressive behaviour and an unfavourable prognosis.

CD44-Deficient Mice Develop Normally with Changes in Subpopulations and Recirculation of Lymphocyte Subsets

Cell adhesion molecules are considered to be pivotal elements required for proper embryo development. The transmembrane glycoprotein CD44, which is expressed in numerous splice variants on the surface of many different cell types and tissues, has been suggested to be involved in several physiological processes such as cell-cell interactions, signal transduction, and lymphocyte homing and trafficking during embryogenesis and in the adult organism. Some splice variants are thought to play an important role in tumor progression. To investigate the physiological roles of CD44 in vivo, we abolished expression of all isoforms of CD44 in mice by targeted insertion of a lacZ/neo cassette into the reading frame of the leader peptide. CD44-deficient mice are viable without obvious developmental defects and show no overt abnormalities as adults. However, CD44-deficient lymphocytes exhibit impaired entry into the adult thymus, although lymphocyte development is apparently unaltered. Our data indicate that all splice variants of CD44 are dispensable for embryonic development and implicate a critical function for CD44 in lymphocyte recirculation.

Fetal development after transfer is increased by replacing protein with the glycosaminoglycan hyaluronan for mouse embryo culture and transfer

The effect of macromolecules on mouse embryo development and viability after culture in sequential media was investigated. It was found that high rates of viable blastocysts could be obtained in the absence of any macromolecule. Blastocyst cell numbers were increased when bovine serum albumin was present in the culture medium, although this benefit was not manifest after blastocyst transfer. Rather, the highest rates of implantation and fetal development after blastocyst transfer were observed when hyaluronan was the macromolecule in the culture media. Subsequent analysis revealed that the beneficial effects of hyaluronan were due to its presence in the transfer medium. As the highest cell numbers and hatching rates obtained in this study occurred when both serum albumin and hyaluronan were present in the same medium, it is proposed that embryo culture media should contain both serum albumin and hyaluronan, while the transfer medium need only contain hyaluronan.

Adhesion proteins in the biology of breast cancer: contribution of CD44

One of the most important features of tumor cell invasion is the ability to establish or modulate adhesion to other cells or to an extracellular matrix, a process mediated by a large number of adhesion proteins. This review examines how CD44 participates in malignant transformation and progression of the breast epithelium. CD44 is a family of cell adhesion glycoproteins generated by alternative splicing of up to 10 variant exons. Discrete CD44 isoforms are overexpressed in different human cancers, including breast cancer. Recent studies, including our own, have shown that CD44 is involved in two of the three steps of the invasive cascade: adhesion to the extracellular matrix and motility. The overexpression of one of the CD44 variants, CD44v6, is a significant component in the malignant transformation of the breast epithelium and its use as a prognostic marker is presently investigated.

CD44 modulates Hs578T human breast cancer cell adhesion, migration, and invasiveness

CD44 is an adhesion molecule that has been implicated in tumor progression of epithelial and nonepithelial tumors. One of its variants, CD44v6, is involved in the production of experimental metastasis. Previous reports have indicated that in human breast cancer the overexpression of CD44, and moreover the presence of CD44v6, correlated with poor prognosis. This study focuses on the role of these molecules in in vitro invasion of breast cancer cells. The effect of antibodies against all CD44 isoforms and CD44v6 was evaluated in different in vitro experimental assays that are closely related to tumor cell invasion in vivo: adhesion to hyaluronan and purified extracellular matrix components; cell motility; haptotaxis; and invasion of purified extracellular matrix components. The highly metastatic human breast cancer cell line Hs578T was used in all assays. Our results show that both antibodies have a blocking effect on cell migration, on haptotatic migration, on in vitro invasion, and on adhesion to hyaluronan and purified extracellular matrix components. In conclusion, our data show that, in addition to its participation in adhesion to components of the extracellular matrix, CD44v6 is involved in the motility and in invasion of tumoral cells.

Non-isotopic in situ hybridization of CD44 transcript in formalin-fixed paraffin-embedded sections

We established a protocol for the non-isotopic in situ detection of adhesion molecule CD44 messenger RNA (mRNA) in archival formalin-fixed paraffin-embedded sections of human surgical materials. Four brain tumor samples with different histopathologies (a metastatic adenocarcinoma, a metastatic squamous carcinoma, a glioblastoma and a craniopharyngioma) were thus studied using a 157 nt digoxigenin-labeled RNA probe complementary to the common mRNA region to all the CD44 isoforms. The CD44 transcript was detected in the cytoplasm of glioma and such epithelial tumor cells as metastatic carcinoma and craniopharyngioma. A competitive hybridization study confirmed the specificity of the CD44 probe. The optimization of critical conditions are also discussed. This protocol should therefore be useful in making an accurate evaluation of mRNA localization and may also facilitate the successful completion of extensive retrospective studies on a large number of archival samples.